CVE-2026-74262 kcm: use WRITE_ONCE() when changing lower socket callbacks
A race condition in the Linux kernel's KCM module can cause stale or misdirected wakeups due to unsynchronized socket callback updates.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-74262?
CVE-2026-74262 is a high-severity vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
kcm: use WRITE_ONCE() when changing lower socket callbacks
kcm_attach() replaces a live lower TCP socket's sk_data_ready and sk_write_space callbacks with KCM handlers, and kcm_unattach() restores them later. Those callback-pointer updates are still plain stores even though the same fields can be read and invoked concurrently on other CPUs.
If another CPU observes an older callback snapshot after the live field has already been restored, callback execution can run with a mismatched target and sk_user_data state, leading to stale or misdirected wakeups.
Use WRITE_ONCE() for the callback replacement and restore operations so these shared callback fields follow the same visibility contract already established by the earlier 4022 fixes.
Which versions are affected by CVE-2026-74262?
How do I fix CVE-2026-74262?
Apply the vendor's patch.
Is CVE-2026-74262 being exploited?
There is no known exploitation of CVE-2026-74262 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-74262, DEBIAN-CVE-2026-74262, GHSA-rv7w-h679-g92g, UBUNTU-CVE-2026-74262.